feat: populate email templates at delivery time, add plaintext defaults

[mattbonnell]

Related issue

#1065

• Persist serialized template models in Messages
• Add plaintext templates for "text/plain" portion of email body
• Store populated plaintext templates in Message in DB (for auditing purposes), populate HTML templates at send-time

Proposed changes

Checklist

• I have read the contributing guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security. vulnerability, I
  confirm that I got green light (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further comments

[aeneasr]

LMK when good for another 👀

[aeneasr]

I have resolved the e2e tests so this should work again - rerunning tests now.

[aeneasr]

e2e test pass on master again, so the failures here are related to the changes in the PR

[mattbonnell]

e2e test pass on master again, so the failures here are related to the changes in the PR

yep, need to fix some things related to the e2e tests.

[mbonnell-wish]

Hey @aeneasr, I'm wondering - do you think we need the plaintext portion of the email at all, or can we just drop that?

[aeneasr]

Yes, many email clients reject HTML versions as spam or do not display them correctly!

[mattbonnell]

Yes, many email clients reject HTML versions as spam or do not display them correctly!

okay cool, will keep plugging away on this one.

[mattbonnell]

seems something wonky is going on with the sdk

[mattbonnell]

@aeneasr ready for another review :)

[aeneasr]

🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉

[mattbonnell]

Thanks for the reviews, as always! Do you think we'll see this in v0.6?

[aeneasr]

Yes of course :)